From: Davidlohr Bueso <dave@stgolabs.net>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-scsi@vger.kernel.org,
"James E.J. Bottomley" <jejb@linux.ibm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
GR-QLogic-Storage-Upstream@marvell.com,
Hannes Reinecke <hare@suse.de>, Javed Hasan <jhasan@marvell.com>,
Saurav Kashyap <skashyap@marvell.com>,
Thomas Gleixner <tglx@linutronix.de>,
Davidlohr Bueso <dbueso@suse.de>
Subject: Re: [PATCH 4/4] scsi: bnx2fc: Avoid using get_cpu() in bnx2fc_cmd_alloc().
Date: Fri, 6 May 2022 21:46:50 -0700 [thread overview]
Message-ID: <20220507044650.q3rcdi3mzlfvp37i@offworld> (raw)
In-Reply-To: <20220506105758.283887-5-bigeasy@linutronix.de>
On Fri, 06 May 2022, Sebastian Andrzej Siewior wrote:
>Using get_cpu() leads to disabling preemption and in this context it is
>not possible to acquire the following spinlock_t on PREEMPT_RT because
>it becomes a sleeping lock.
>
>Commit
> 0ea5c27583e1c ("[SCSI] bnx2fc: common free list for cleanup commands")
>
>says that it is using get_cpu() as a fix in case the CPU is preempted.
>While this might be true, the important part is that it is now using the
>same CPU for locking and unlocking while previously it always relied on
>smp_processor_id().
>The date structure itself is protected with a lock so it does not rely
>on CPU-local access.
>
>Replace get_cpu() with raw_smp_processor_id() to obtain the current CPU
>number which is used as an index for the per-CPU resource.
>
>Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
next prev parent reply other threads:[~2022-05-07 4:58 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-06 10:57 [PATCH 0/4] scsi: PREEMPT_RT related fixes Sebastian Andrzej Siewior
2022-05-06 10:57 ` [PATCH 1/4] scsi: fcoe: Add a local_lock to fcoe_percpu Sebastian Andrzej Siewior
2022-05-06 10:57 ` [PATCH 2/4] scsi: fcoe: Use per-CPU API to update per-CPU statistics Sebastian Andrzej Siewior
2022-05-10 0:48 ` Davidlohr Bueso
2022-05-06 10:57 ` [PATCH 3/4] scsi: libfc: Remove get_cpu() semantics in fc_exch_em_alloc() Sebastian Andrzej Siewior
2022-05-06 10:57 ` [PATCH 4/4] scsi: bnx2fc: Avoid using get_cpu() in bnx2fc_cmd_alloc() Sebastian Andrzej Siewior
2022-05-07 4:46 ` Davidlohr Bueso [this message]
2022-05-17 1:28 ` [PATCH 0/4] scsi: PREEMPT_RT related fixes Martin K. Petersen
2022-05-17 6:11 ` Sebastian Andrzej Siewior
2022-05-20 1:09 ` Martin K. Petersen
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